The present invention relates to models utilized in restorative dentistry in general, and more particularly to an improvement in arrangements which permit coupling and separation as well as replacement of a denial die on a cast base.
It has been well known in restorative dentistry to form an impression of a dentition to be restored and then reproduce such dentition in the form of a dental model made from plaster, artificial stone or the like. After the dental model has been accurately formed it is necessary to cut the dental model into sections which represent one or more teeth needing correction or to be used for the formation of a prosthesis. The problem, however, is that the segments or dies must be often removed and replaced from its cast base without disturbing adjacent segments or damaging its own form. Also, the die should be indexed in the model to be repositioned with great accuracy after removal. Various means for removably coupling such model segments or dies to the cast base have been proposed. Typically, various pin systems have been employed, which utilize pins fixed in a die and projecting outwardly therefrom. Such pins are received in holes provided for this purpose in the cast base.
Dowel pins are frequently employed for coupling the dies to the cast base. These pins are initially positioned over an impression tray and maintained suspended over the tray. The material of the model is then poured into the impression tray to form the dental model or full cast of the prepared teeth to be worked on. While the plaster, or other comparable material, is in a soft state this material will fully surround the pins to embed the same in the model. After the model has hardened the stems of the dowel pins will project outwardly from the model. After the model has fully hardened with the pins projecting therefrom, a separator medium, such as "Vaseline" is placed on the lower surface of the model. Thereupon, additional stone or plaster material is poured on or applied to the lower wall of the model to form a cast base. The cast base and the model are fully hardened and cured. As a result, holes are formed in the cast base at the locations of the stems of the dowel pins. These holes conform to the contours of the pins. The model is then cut by a saw into segments or dies as described herein above. The dies with the pins can then be separated and removed from the cast base to be worked on and reinserted into the base. When the die is replaced into the base the pins are aligned in the corresponding receiving holes.
Prior to pouring the base, sleeves may be placed over the projecting pins and the sleeves are then cast into the base. The segments with the projecting pins can then be inserted and removed from the sleeves.
The PINDEX.RTM. System by the Whaledent Company has been, for example, developed for the orientation of the placement of removable dies into the cast. Such system is disclosed in U.S. Pat. No. 3,704,519. In the system of this patent, holes are provided in the removable part of the model. Pins with sleeves or bushings on them are inserted and pressed into the dental model. The stone is then poured on to the bushings as sleeves and the bushings or sleeves are cast into the base. The dies may be removed by pulling the pins from the bushings. At least two pins are necessary, for each die to ensure proper orientation and replacement of the die segments into the cast.
While the PINDEX.RTM. system has been widely accepted and used, it would appear to be desirable to have a system which would require only a single insertion and yet achieve the benefits of the PINDEX.RTM. system.